Does Shredder work with Stock damage?
The Shredder ability causes damage to weaken an enemy's armor. Stocks ensure that if you miss, you cause damage.
If you miss, and the Stock does damage, does this then cause the Shredder effect?
Solution 1:
No. Damage from stocks is applied without regard to armor (e.g., a Superior Stock does 3 damage directly to HP, bypassing all armor). Accordingly they will not shred armor.
Source: I've brought a Grenadier with Shredder and a stock equipped to dozens of missions.